Facebook's CFO said in November the company expected to see its ad sales growth rate "come down meaningfully" in 2017.

It's not for lack of growth in its audience. Facebook announced hitting two billion monthly users during the quarter, putting it miles ahead of social media rivals like Twitter. But Facebook is reaching its limit for the number of ads it can place in those users' news feeds.

In the absence of limitless ad sales growth on Facebook proper, the company must now lean more on its other popular products. Those include apps like Instagram, WhatsApp and Messenger, two of which have more than a billion users.

Facebook has begun ramping up advertising on Instagram and Messenger, but has yet to disclose sales figures for either product.

On a conference call with analysts Wednesday, Facebook CEO Mark Zuckerberg said he'd like to see the company "move a little faster" in making money from Messenger in particular.

Investors had been bracing for even more of a slowdown ahead of the earnings report. Facebook stock ticked up 4% in after hours trading Wednesday.